Eukaryotic-type carbonic anhydrase; Carbonic anhydrases are zinc metalloenzymes which catalyse the reversible hydration of carbon dioxide to bicarbonate.. CAs have essential roles in facilitating the transport of carbon dioxide and protons in the intracellular space, across biological membranes and in the layers of the extracellular space; they are also involved in many other processes, from respiration and photosynthesis in eukaryotes to cyanate degradation in prokaryotes. There are five known evolutionarily distinct CA families (alpha, beta, gamma, delta and epsilon) that have no significant sequence identity and have structurally distinct overall folds. Some CAs are membrane-bound, while others act in the cytosol; there are several related proteins that lack enzymatic activity. The active site of alpha-CAs is well described, consisting of a zinc ion coordinated through 3 histidine residues and a water molecule/hydroxide ion that acts as a potent nucleophile. The enzyme employs a two-step mechanism: in the first step, there is a nucleophilic attack of a zinc-bound hydroxide ion on carbon dioxide; in the second step, the active site is regenerated by the ionisation of the zinc-bound water molecule and the removal of a proton from the active site. Beta- and gamma-CAs also employ a zinc hydroxide mechanism, although at least some beta-class enzymes do not have water directly coordinated to the metal ion.

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gi 2217307355   60 GGTRQSPINIQWRDSVYDPQLKPLRVSYEAASCLYIWNTGYLFQVEFDDAT 110
Cdd:smart01057  21 GGKRQSPIDIVTAEAQYDPSLKPLKLSYDQPTAKRILNNGHTVQVNFDDDG 71

Carbonic anhydrase [Inorganic ion transport and metabolism];

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gi 2217307355  61 GTRQSPINIqwRDSVyDPQLKPLRVSYEAAScLYIWNTGYLFQVEFDDA 109
Cdd:COG3338    52 GKNQSPIDI--RTAI-KADLPPLKFDYKPTP-LEIVNNGHTIQVNVDPG 96

Eukaryotic-type carbonic anhydrase; Carbonic anhydrases are zinc metalloenzymes which catalyse the reversible hydration of carbon dioxide to bicarbonate.. CAs have essential roles in facilitating the transport of carbon dioxide and protons in the intracellular space, across biological membranes and in the layers of the extracellular space; they are also involved in many other processes, from respiration and photosynthesis in eukaryotes to cyanate degradation in prokaryotes. There are five known evolutionarily distinct CA families (alpha, beta, gamma, delta and epsilon) that have no significant sequence identity and have structurally distinct overall folds. Some CAs are membrane-bound, while others act in the cytosol; there are several related proteins that lack enzymatic activity. The active site of alpha-CAs is well described, consisting of a zinc ion coordinated through 3 histidine residues and a water molecule/hydroxide ion that acts as a potent nucleophile. The enzyme employs a two-step mechanism: in the first step, there is a nucleophilic attack of a zinc-bound hydroxide ion on carbon dioxide; in the second step, the active site is regenerated by the ionisation of the zinc-bound water molecule and the removal of a proton from the active site. Beta- and gamma-CAs also employ a zinc hydroxide mechanism, although at least some beta-class enzymes do not have water directly coordinated to the metal ion.

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                   ....*....|....*....|....*....|....*....|....*....|.
gi 2217307355   60 GGTRQSPINIQWRDSVYDPQLKPLRVSYEAASCLYIWNTGYLFQVEFDDAT 110
Cdd:smart01057  21 GGKRQSPIDIVTAEAQYDPSLKPLKLSYDQPTAKRILNNGHTVQVNFDDDG 71

Carbonic anhydrase alpha (vertebrate-like) group. Carbonic anhydrases (CAs) are zinc-containing enzymes that catalyze the reversible hydration of carbon dioxide in a two-step mechanism: a nucleophilic attack of a zinc-bound hydroxide ion on carbon dioxide, followed by the regeneration of the active site by ionization of the zinc-bound water molecule and removal of a proton from the active site. They are ubiquitous enzymes involved in fundamental processes like photosynthesis, respiration, pH homeostasis and ion transport. There are three evolutionary distinct groups - alpha, beta and gamma carbonic anhydrases - which show no significant sequence identity or structural similarity. Most alpha CAs are monomeric enzymes. The zinc ion is complexed by three histidine residues and a fourth conserved histidine plays a potential role in proton transfer.

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                  ....*....|....*....|....*....|....*....|....*...
gi 2217307355  61 GTRQSPINIQWRDSVYDPQLKPLRVSYEAASCLYIWNTGYLFQVEFDD 108
Cdd:cd00326     1 GKRQSPINIVTSAVVYDPSLPPLNFDYYPTTSLTLVNNGHTVQVNFDD 48

Carbonic anhydrase alpha, isozymes I, II, and III and XIII. Carbonic anhydrases (CAs) are zinc-containing enzymes that catalyze the reversible hydration of carbon dioxide in a two-step mechanism: a nucleophilic attack of a zinc-bound hydroxide ion on carbon dioxide, followed by the regeneration of the active site by ionization of the zinc-bound water molecule and removal of a proton from the active site. They are ubiquitous enzymes involved in fundamental processes like photosynthesis, respiration, pH homeostasis and ion transport. Most alpha CAs are monomeric enzymes. The zinc ion is complexed by three histidines. This vertebrate subgroup comprises isozymes I, II, and III, which are cytoplasmic enzymes. CA I, for example, is expressed in erythrocyes of many vertebrates; CA II is the most active cytosolic isozyme; while it is being expressed nearly ubiquitously, it comprises 95% of the renal carbonic anhydrase and is required for renal acidification; CA III has been implicated in protection from the damaging effect of oxidizing agents in hepatocytes. CAXIII may play important physiological roles in several organs.

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gi 2217307355  61 GTRQSPINIQWRDSVYDPQLKPLRVSYEAASCLYIWNTGYLFQVEFDDATEAS 113
Cdd:cd03119    25 GDRQSPIDIKTKDAKHDPSLKPLSVSYDPATAKTILNNGHSFNVEFDDTDDRS 77

Carbonic anhydrase alpha, prokaryotic-like subfamily. Carbonic anhydrases (CAs) are zinc-containing enzymes that catalyze the reversible hydration of carbon dioxide in a two-step mechanism: a nucleophilic attack of a zinc-bound hydroxide ion on carbon dioxide, followed by the regeneration of the active site by ionization of the zinc-bound water molecule and removal of a proton from the active site. They are ubiquitous enzymes involved in fundamental processes like photosynthesis, respiration, pH homeostasis and ion transport. Most alpha CAs are monomeric enzymes. The zinc ion is complexed by three histidines. This sub-family includes bacterial carbonic anhydrase alpha, as well as plant enzymes such as tobacco nectarin III and yam dioscorin and, carbonic anhydrases from molluscs, such as nacrein, which are part of the organic matrix layer in shells. Other members of this family may be involved in maintaining pH balance, in facilitating transport of carbon dioxide or carbonic acid, or in sensing carbon dioxide levels in the environment. Dioscorin is the major storage protein of yam tubers and may play a role as an antioxidant. Tobacco Nectarin may play a role in the maintenace of pH and oxidative balance in nectar. Mollusc nacrein may participate in calcium carbonate crystal formation of the nacreous layer. This subfamily also includes three alpha carbonic anhydrases from Chlamydomonas reinhardtii (CAH 1-3). CAHs1-2 are localized in the periplasmic space. CAH1 faciliates the movement of carbon dioxide across the plasma membrane when the medium is alkaline. CAH3 is localized to the thylakoid lumen and provides CO2 to Rubisco.

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gi 2217307355  61 GTRQSPINIQWRDSVYDpQLKPLRVSYEAAScLYIWNTGYLFQVEFDDA 109
Cdd:cd03124    18 GKNQSPIDITTKAVVSD-KLPPLNYNYKPTS-ATLVNNGHTIQVNFEGN 64

Carbonic anhydrase alpha related protein: groups X, XI and related proteins. This subgroup contains carbonic anhydrase related proteins (CARPs) X and XI, which have been implicated in various biological processes of the central nervous system. CARPs are sequence similar to carbonic anhydrases. Carbonic anhydrases are zinc-containing enzymes that catalyze the reversible hydration of carbon dioxide in a two-step mechanism. CARPs have lost conserved histidines involved in zinc binding and consequently their catalytic activity. CARP XI plays a role in the development of gastrointestinal stromal tumors.

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gi 2217307355  61 GTRQSPINIQWRDSVYDPQLKPLRVSYEAASCLYIWNTGYLFQVEFDDAT 110
Cdd:cd03121    18 GRRQSPVDIEPSRLLFDPFLTPLRIDTGRKVSGTFYNTGRHVSFRPDKDP 67

Carbonic anhydrase alpha related protein, group VIII. Carbonic anhydrase related proteins (CARPs) are sequence similar to carbonic anhydrases. Carbonic anhydrases are zinc-containing enzymes that catalyze the reversible hydration of carbon dioxide in a two-step mechanism. CARPs have lost conserved histidines involved in zinc binding and consequently their catalytic activity. CARP VIII may play roles in various biological processes of the central nervous system, and could be involved in protein-protein interactions. CARP VIII has been shown to bind inositol 1,4,5-triphosphate (IP3) receptor type I (IP3RI), reducing the affinity of the receptor for IP3. IP3RI is an intracellular IP3-gated Ca2+ channel located on intracellular Ca2+ stores. IP3RI converts IP3 signaling into Ca2+ signaling thereby participating in a variety of cell functions.

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gi 2217307355  61 GTRQSPINIQWRDSVYDPQLKPLRVSYEAASC--LYIWNTGYLFQVEF 106
Cdd:cd03120    13 GEYQSPINLNSREARYDPSLLEVRLSPNYVVCrdCEVINDGHTIQIIL 60